The British government wants to require porn websites to verify their users are adults. The effort is being watched by other countries hoping to better regulate pornographic content but has raised concerns about privacy, censorship, and competition. It has run into multiple delays that reflect the confusion surrounding it.

“It’s a mess,” said Jim Killock, of the London-based Open Rights Group, a digital civil liberties group.

Killock says the government’s blueprints for its online “porn block” don’t do enough to protect personal data. Others believe the plan amounts to economic censorship. And many fear the rules would effectively give more power to a little known company that dominates the internet porn industry.

Under the plan, which is now expected to come into force late this year, British porn site visitors will be asked to prove they are 18 or older. Options to do so would include buying a card with an access code in a shop, where they will have to show photo ID, or going online to submit a copy of a passport or driver’s license or use a credit card.

The British government isn’t operating the system itself. Instead, it’s being outsourced to private companies, which can sell their own age verification technology to porn sites. Oversight, meanwhile, has been handed to the British Board of Film Classification, a film ratings and censorship body akin to the Motion Picture Association of America.

Privacy campaigners worry that handing over personal information to access adult sites means a person’s porn viewing habits can be tracked. Those fears are compounded by the lack of privacy and security standards for age verification providers. Instead, there’s a voluntary certification with vague and imprecise requirements.

One age verification provider, 18+, has said it won’t apply for the certificate because its digital wallet system wouldn’t be recognized.

“There are huge privacy concerns with how the data will be held, because the sort of information that people will have to be giving up is highly personal,” said Myles Jackman, a London-based lawyer. Also, “there is a risk that that data will be hacked, breached, stolen, or published in the public domain.”

Critics point to data breaches at adult-oriented websites, notably a high-profile hack at infidelity site Ashley Madison that exposed personal details of millions of users.

They note that tech-savvy youngsters will figure out how to how to evade restriction by using, for example, virtual private networks. And there’s a loophole exempting social media sites such as Twitter, where plenty of smutty content is now found.

The film board acknowledges that “age-verification is not a silver bullet,” but it will stop kids inadvertently coming across inappropriate material. “Determined teenagers will find ways to access pornography.”

There’s also the question of how the new rules would be enforced on the many porn sites based outside the U.K. The film board says it could ask payment providers to withdraw their services and U.K. internet service providers to block them.

Jackman said the result could be “economic censorship,” because smaller, independent British porn producers that can’t afford to comply would simply shut down.

Online porn is a huge industry, but estimates of its size are notoriously hard to come by and there’s no official data. Pornhub, the world’s most popular adult site, is the 16th most visited in the U.K., according to Amazon’s Alexa web analytics .

Further raising concerns about the new system, one of the first age verification systems, AgeID, is owned by a multinational, MindGeek, which is widely recognized as the owner also of some of the most popular adult websites, including YouTube-like portals such as Pornhub, YouPorn, and Redtube.

In response to a consultation by the film board, numerous people and groups said they were concerned that a company responsible for providing so much pornography online would also become a gatekeeper that potentially allows it access to reams of user data.

“There’s a clear conflict of interest,” said Killock. “The fact is they’re effectively creating the Facebook login of porn,” and will get “vast market intelligence” on their rivals and users on competing websites, said Killock, whose group in 2017 unearthed emails from MindGeek executives lobbying British officials to block rival porn sites.

Angie Rowntree, a director and founder of U.S. erotic site Sssh.com, said her company no longer uploads promo clips to Pornhub but many others continue to do business with MindGeek because its sites get an enormous amount of traffic.

“There’s a real risk of MindGeek monopolizing the U.K. segment of adult traffic to an even greater extent than they already do, by virtue of having some of the world’s best known and most popular free porn sites,” she said.

MindGeek spokesman Jim Clark says the company is merely responding to a market opening.

“AgeID is not responsible for the creation of the law, nor is AgeID endorsed by the U.K. government. We have simply developed a product in response to the law,” Clark said by email.

Clark said AgeID doesn’t track users, has “data minimization, security, and privacy at its core,” and is designed not to see or store data, making it less tempting for hackers. And, he says, it won’t be the only choice of age verification on MindGeek websites.

Other countries mulling regulation are watching Britain amid concerns that easy access to porn can warp children’s view of sex.

Lawmakers in Ireland say they’ll examine the British model, after two teenage boys were convicted last week of the murder of 14-year-old Ana Kriegel in a case that shocked the country. One boy was also convicted of violently sexually assaulting her and was found to have thousands of pornographic images on two mobile phones, news reports said.

Britain’s porn firewall was set to take effect on July 15 but an administrative error delayed it by six months. The digital secretary, Jeremy Wright, vows it will eventually come into force.

“There are also those who do not want those measures to be brought in at all,” Wright told lawmakers. “Age verification for online porn needs to happen.”